linux-kernel - Re: [BUG 2.6.29_rc8] BIOS Bug: CPU MTRRs don't cover all of memory, losing 0MB of RAM.

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Date:	Mon, 16 Mar 2009 22:17:13 +0200
From:	Ozan Çağlayan <ozan@...dus.org.tr>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [BUG 2.6.29_rc8] BIOS Bug: CPU MTRRs don't cover all of memory,
 	losing 0MB of RAM.

Yinghai Lu wrote:

> can you check tip/master?
> 
> http://people.redhat.com/mingo/tip.git/readme.txt
> 
> and post boot log.

I compiled tip/master with the same configuration. Here's the head of the dmesg:
(BTW, I'm not getting this backtrace with 2.6.25.20. I know its rather old but maybe
it will help)

---

Initializing cgroup subsys cpuset
Linux version 2.6.29-rc8-tip-tip (root@...nson) (gcc version 4.3.2 (Pardus Linux) ) #1 SMP Mon Mar 16 21:26:14 EET 2009
KERNEL supported cpus:
  Intel GenuineIntel
  AMD AuthenticAMD
  NSC Geode by NSC
  Cyrix CyrixInstead
  Centaur CentaurHauls
  Transmeta GenuineTMx86
  Transmeta TransmetaCPU
  UMC UMC UMC UMC
BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000000 - 000000000009f400 (usable)
 BIOS-e820: 000000000009f400 - 00000000000a0000 (reserved)
 BIOS-e820: 00000000000f0000 - 0000000000100000 (reserved)
 BIOS-e820: 0000000000100000 - 00000000cfd43000 (usable)
 BIOS-e820: 00000000cfd43000 - 00000000cfd4c000 (ACPI data)
 BIOS-e820: 00000000cfd4c000 - 00000000cfd4d000 (usable)
 BIOS-e820: 00000000cfd4d000 - 00000000d0000000 (reserved)
 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fed00000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee10000 (reserved)
 BIOS-e820: 00000000ffc00000 - 0000000100000000 (reserved)
 BIOS-e820: 0000000100000000 - 000000082ffff000 (usable)
DMI 2.5 present.
last_pfn = 0x82ffff max_arch_pfn = 0x1000000
MTRR default type: uncachable
MTRR fixed ranges enabled:
  00000-9FFFF write-back
  A0000-BFFFF uncachable
  C0000-FFFFF write-protect
MTRR variable ranges enabled:
  0 base 0000000000 mask 0000000000 write-back
  1 base 00CFF00000 mask FFFFF00000 uncachable
  2 base 00D0000000 mask FFF0000000 uncachable
  3 base 00E0000000 mask FFE0000000 uncachable
  4 base 0000004000 mask FFFFFFF000 uncachable
  5 base 0000005000 mask FFFFFFF000 uncachable
  6 base 0000006000 mask FFFFFFF000 uncachable
  7 base 0000007000 mask FFFFFFF000 uncachable
x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106
  get_mtrr: cpu0 reg00 base=0000000000 size=0010000000 write-back
  get_mtrr: cpu0 reg01 base=00000cff00 size=0000000100 uncachable
  get_mtrr: cpu0 reg02 base=00000d0000 size=0000010000 uncachable
  get_mtrr: cpu0 reg03 base=00000e0000 size=0000020000 uncachable
  get_mtrr: cpu0 reg04 base=0000000004 size=0000000001 uncachable
  get_mtrr: cpu0 reg05 base=0000000005 size=0000000001 uncachable
  get_mtrr: cpu0 reg06 base=0000000006 size=0000000001 uncachable
  get_mtrr: cpu0 reg07 base=0000000007 size=0000000001 uncachable
e820 update range: 0000000000004000 - 0000000000008000 (usable) ==> (reserved)
e820 update range: 00000000cff00000 - 0000000100000000 (usable) ==> (reserved)
WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 0MB of RAM.
------------[ cut here ]------------
WARNING: at arch/x86/kernel/cpu/mtrr/cleanup.c:1079 mtrr_trim_uncached_memory+0x2a9/0x2cd()
Hardware name: ProLiant DL580 G5
Modules linked in:
Pid: 0, comm: swapper Not tainted 2.6.29-rc8-tip-tip #1
Call Trace:
 [<c0133871>] warn_slowpath+0x71/0xa8
 [<c011e23a>] ? default_spin_lock_flags+0x9/0xb
 [<c03aad3c>] ? _spin_unlock_irqrestore+0x17/0x1b
 [<c011e23a>] ? default_spin_lock_flags+0x9/0xb
 [<c03aad3c>] ? _spin_unlock_irqrestore+0x17/0x1b
 [<c0133edd>] ? release_console_sem+0x176/0x1a3
 [<c0134358>] ? vprintk+0x276/0x299
 [<c03a87cc>] ? printk+0xf/0x13
 [<c054aece>] mtrr_trim_uncached_memory+0x2a9/0x2cd
 [<c0545cf5>] setup_arch+0x43c/0x9ab
 [<c0133edd>] ? release_console_sem+0x176/0x1a3
 [<c0134358>] ? vprintk+0x276/0x299
 [<c0134358>] ? vprintk+0x276/0x299
 [<c0548759>] ? __reserve_early+0xe4/0xf8
 [<c03a87cc>] ? printk+0xf/0x13
 [<c0543580>] start_kernel+0x77/0x323
 [<c0543085>] __init_begin+0x85/0x8d
---[ end trace 4eaa2a86a8e2da22 ]---
update e820 for mtrr

-- 

Ozan Çağlayan
<ozan_at_pardus.org.tr>
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